That should effectively remove carriage returns, line breaks, semicolons and quotation marks from any field in the userinfo string (Client names are kept in their userinfo string)

EDIT: Silly me, you should also perform this check in the say function (G_Say or something in g_cmds.c)

EDIT: I suppose the semi-logical thing would be to remove all instances of those characters in the string, and afterwards check if there are any characters remaining in the string (To prevent a free method of getting a blank name/etc)